1. Field of the Invention
This invention relates to the field of processes for preparing acyclic carboxylic acids and, more particularly, to such processes featuring the reaction of an olefinic compound and carbon monoxide in the presence of palladium-containing catalyst (i.e., carbonylation).
2. Description of the Prior Art
The C.sub. 4 and C.sub. 5 carboxylic acids, e.g., 3-butenoic acid (vinylacetic acid), crotonic acid, butyric acid, isobutyric acid, glutaric acid and methyl succinic acid are industrially important compounds useful as intermediates for the manufacture of numerous chemical products. It is known at present that carboxylic acids and/or carboxylic acid esters can be prepared by the reaction of an olefinically unsaturated compound and carbon monoxide (i.e., carbonylation) in the presence of palladium-containing catalysts. U.S. Pat. No. 3,427,344 to Tsuji, et al. describes the reaction of allyl alcohol with carbon monoxide in the presence of palladium chloride catalyst. Among the products formed are ethyl-3-butenoate and 3-butenoic anhydride. U.S. Pat. No. 3,437,676 to von Kutepow, et al. describes the reaction of allyl alcohol, carbon monoxide and water in the presence of a homogenous palladium complex such as bistriphenylphosphine palladium dichloride to provide carboxylic acids. U.S. Pat. No. 4,140,806 to Fernholz, et al. describes the reaction of an allyl compound substituted by oxygen functions, e.g., allyl alcohol, with carbon monoxide in the presence of a heavy metal catalyst such as elemental palladium and methyl iodide or palladium iodide as co-catalyst to provide vinylacetic acid. Patentees disclose that isometric C.sub.4 acids, such as cis- and trans- crotonic acid, are not formed, or form in a small amount only, in contrast to known proceses. U.S. Pat. No. 4,189,608 to Kurkov describes the reaction of allyl alcohol with carbon monoxide in the presence of a palladium chloride catalyst and in a substantially anhydrous C.sub.2 -C.sub.10 carboxylic acid liquid solvent to provide 3-butenoic acid (i.e., vinylacetic acid).